Mark Zuckerberg In Alex Volkanovski's Corner At UFC 298, Share Pre-Fight Hug

Mark Zuckerberg may be worth $160+ billion, but he's not above working a weekend side gig ... the Facebook founder spent Saturday night cornering Alex Volkanovski for his title fight at UFC 298!

Well, at least until the punches started flying.

Zuck and Volk's relationship isn't a secret -- they're buddies -- the guys have hung out/trained together multiple times since MZ got into Brazilian Jiu-Jitsu a couple of years ago.

So, when the 35-year-old featherweight walked to the Octagon at the Honda Center in Anaheim for his main event scrap vs. Ilia Topuria, Zuckerberg, in full coach's kit, was standing with Alex's team waiting for the fighter.

AV and MZ even shared a hug before Volk stepped in the cage.

It then appeared Zuckerberg took an Octagon-side seat ... and watched as a spectator, no doubt rooting for his friend.

Unfortunately for the pair, the night ended with an "and new" after Volkanovski was stopped by KO in the second round of the 145 lb title fight ... and Topuria was crowned the featherweight champion.

Mark watched the stoppage from just feet away.

Zuckerberg was also front and center earlier in the night when Merab Dvalishvili threw opponent Henry Cejudo down in front of the FB CEO ... and had a mid-round conversation with him, much to the amusement of Mark.

Saturday marks the closest Zuckerberg's gotten to a cage since negotiations with rival Elon Musk broke down ... a battle that at one time looked like it would take place at The Colosseum.